1. Field of the Invention
The present invention relates to an ink jet recording apparatus that records by discharging ink from recording means to a recording material.
2. Related Background Art
A recording apparatus that is provided with the function of a printer, a copying machine, a facsimile machine, or the like, or a recording apparatus that is used as output equipment for complex electronic equipment, a work station, or the like, that includes a computer or a word processor, among other recording apparatuses, is structured to record images (including characters, symbols, or the like) on a recording material (recording medium) such as paper, cloth, a plastic sheet, or an OHP sheet in accordance with image information (recording information). The recording apparatuses are classified into ink jet type, wire-dot type, thermal type, and laser beam type, among some other types, depending on the adopted recording method.
The serial type recording apparatus, which records while performing main scans in a direction intersecting with the conveying direction of a recording material, forms images by discharging ink from a recording head serving as recording means, while it moves (performs main scans) along the recording material, and a sheet feeding of a predetermined amount (pitch conveyance serving as a sub-scanning) is effected subsequent to the completion of image formation of one line portion. Then, the recording (main scanning) of the images of the next portion is performed on the recording material, which is made stationary again. Such operation is repeated to complete the entire recording on the recording material. On the other hand, in the line type recording apparatus, which records only by sub-scanning in the conveying direction of a recording material, the recording material is set at a predetermined recording position, and then, after the recording of one line portion is executed altogether, the sheet feeding of a predetermined amount is effectuated, and the recording of the next line is performed altogether, and by repeating such operation, the recording is made on the recording material entirely.
Among these types of recording apparatuses, the ink jet type recording apparatus (ink jet recording apparatus) performs recording by discharging ink from an ink discharge portion thereof to a recording material, which makes it easier to arrange the recording head compactly for the recording of highly precise images at high speed. Also, there are advantages, among many other advantages, that the recording can be effected on plain paper without special treatment and thus the running cost of the apparatus is made lower, and that, being of non-impact type, the apparatus makes less noise, and, further, color images can be formed with ease by using many kinds of ink (various colors of ink, for example).
For the ink jet recording apparatus that records by discharging ink from the discharge ports formed in recording means to a recording material, there is provided discharge port protection means or discharge recovery process means in order to eliminate clogging of the discharge ports due to dried ink or ink discharge defects due to dust particles, bubbles, or the like in the discharge ports.
The main structure of the discharge port protection means is capping means, which covers a discharge port surface of the recording head serving as recording means by use of a cap formed by elastic material, such as rubber. Also, the main structure of the discharge recovery process means is suction recovery means for removing the causes of ink discharge defects, together with ink, from the inside of the cap by means of the suction or pressure reduction by negative pressure generating means, such as a pump, to forcibly discharge ink from the discharge ports; pre-discharge means that discharges ink from the discharge ports for a purpose other than recording; and wiping means that removes ink and other adhering matter from the discharge port surface, among some other components.
Also, for the negative pressure generating means (suction means) that reduces the inner pressure of the cap, a piston pump, a tube pump, or the like is used. Also, as suction means for removing ink residing in the cap or in the ink flow path formed by a tube or the like after suction, there are mainly two means. A first means is the “cap-open idle suction”, which performs suction while keeping the cap apart from the recording head. For example, cap-open suction means has been proposed in Japanese Patent Application Laid-Open No. 03-093548, in which a cap is released, while being inclined, without any provision of a valve mechanism for atmospheric communication. A second means is the “cap closed idle suction”, which performs suction after the inside of the cap is made to be communicative with the atmosphere by use of the atmosphere communication mechanism provided with a valve capable of keeping the inside of the cap communicative with the atmosphere in a state of being capped. The atmosphere communication mechanism in this case is, in general, structured by a tube communicating with the inside of the cap, and the atmosphere communication valve arranged at the leading end of the tube, which is made freely open or closed. The cap closed idle suction is disclosed in U.S. Pat. No. 5,153,613, for example. Such suction is capable of effecting more reduction of ink remains than the cap-open idle suction.
The cap-open idle suction makes it easier to provide the suction mechanism smaller at lower costs, but has drawbacks, such as ink in the cap may drip into the recording apparatus, because the cap is almost in the horizontal posture when it is open to discharge ink substantially in the horizontal direction, for example.
Moreover, along with the enhancement of image quality that has been increasing in demand, the precision of ink discharge position becomes more important in recent years, and thus, in terms of the discharge stabilization, the discharge ports of a recording head tend to be installed almost horizontally to enable ink to be discharged downward vertically. Such a mechanism is now considered to be common. In such a mechanism, if a cap is released diagonally from the opposite side of the suction port provided thereon in order to induce the air into the cap, the suction port of the cap is positioned on the upper side of the cap thus inclined (on the side higher in the vertical direction). As a result, a drawback is encountered such as to make it difficult to suck ink from the inside of the cap by a pump for the sufficient removal of ink.
Particularly, in a case of pigment ink, if the cap absorbent formed by a material having large pore diameters is used for the prevention of clogging, the propagating speed of pigment ink in the ink absorbent is made slower (the ink propagation becomes difficult). As a result, if the posture of the cap is arranged so as to position the suction port to be on the lower side of the inclination as described earlier, a drawback that the capability of ink collection is made extremely low may be encountered.
Then, if ink is not removed from inside the cap sufficiently, ink is caused to adhere to the discharge port surface in the succeeding operations, such as the next opening or closing of the cap. Consequently, the ink that has adhered is transferred to the carrier systems or ink spreads greatly when being wiped. Further, ink adheres to the blade, which is accumulated thereon in a short period of time, and brings about a drawback that the wiping performance is made lower, among some other drawbacks.
On the other hand, when using such an atmosphere communication mechanism as the cap closed idle suction, the performance of ink removal capability is high. But, it is unavoidable that not only the cost of the suction means is higher, but also, the size thereof becomes greater. Moreover, when the atmosphere communication mechanism is used, the inside of the atmosphere communication tube is made a negatively pressurized chamber if the suction operation is performed in a state where the atmosphere communication valve is closed. As a result, ink forcibly discharged from the recording head enters the interior of the atmosphere communication mechanism, and the ink thus entered is dried unless the entered ink in the atmosphere communication mechanism is discharged exactly by the idle suction that follows immediately thereafter. Thus, a drawback is encountered such as eventual clogging of the atmosphere communication port in some cases.